Roof supports for mine workings



Dec. 31, 1968 V K. M. GROETSCHEL 3,418,814

ROOF SUPPORTS FOR, MINE WORKINGS Sheet Filed March 3, 1967 Zbd 1968 K. M. GROETSCHEL 3,

ROOF SUPPORTS FOR MINE WORKINGS Filed March 3, 1967 Sheet 2 of 5 22bl 1 226g Dec. 31, 1968 K. M. GROETSCHEL 3,413,814

ROOF SUPPORTS FOR MINE WORKINGS Sheet Filed March 5, 1967 lrWeYH-OY: K'cwL MavLq Gvoetsdzel 3 QOwwe 'l-lou u Rbkovuass United States Patent ice 3,418,814 ROOF SUPPORTS FOR MINE WORKINGS Karl M. Groetschel, 44 Stolzestrasse, 463 Bochum, Germany Filed Mar. 3, 1967, Ser. No. 620,513 Claims priority, application Great Britain, Mar. 4, 18 66, 9,472/ 66 8 Ciairns. (CI. 61-45) ABSTRACT OF THE DISCLOSURE This invention relates to roof supports comprising a base, a plurality of sockets in said base forming prop seatings, a plurality of props in said seatings and a roof engaging superstructure carried by said props, and is concerned with the provision of laterally presented entries in said seatings or any of them and the provision of a powerenergized device for releasable connection to the props or any of them for withdrawal and insertion of the prop concerned through its associated entry.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to roof supports for use in underground mine workings. The invention has been developed for use in coal mines where the method of mining adopted is that known generally as mechanized long wall mining. In this method coal-getting machinery is traversed horizontally along a coal face and coal thus removed from the face is discharged or deflected onto a conveyor which extends along the coal face. The roof of the mine working, extending over the top of the coal-getting machinery and conveyor and in a direction away from the coal face, that is to say on the side of the conveyor remote from the coal face, requires to be supported as the coal face advances with the removal of coal therefrom.

This invention relates specifically to a roof support for use in underground mine workings comprising a base, a plurality of power-operated extensible props thereon, and a roof-engaging superstructure carried by the props. Such supports are herein referred to as being of the kind specified.

In roof supports of the kind specified it is desirable that the props should be supported in stable upstanding and generally perpendicular relation to the base at all times. This is especially so when the props, or certain ones of them, are contracted to lower the superstructure or part thereof since, under these conditions, the prop concerned, or each of them, is not restrained against tilting by virtue of engagement between the superstructure or said part thereof and the roof. Moreover, the prop and superstructure, or said part thereof, may be of substantial weight and in mine workings where the floor (and roof) are inclined to the horizontal this weight accentuates the instability of the prop or props concerned.

It is, however, also desirable that any prop which requires, or is likely to require, periodical testing, maintenance, or servicing shall be capable of being removed from the support to facilitate these operations.

Description of the prior art Hitherto this has been done by forming prop seatings in the base, such seatings being of a size to provide generous lateral clearance with respect to the props which respectively they receive, each of the props concerned being capable of lateral release from the superstructure by provision of prop seatings on the superstructure which either are open at one side so as to allow the upper end of the prop to be moved laterally clear of the superstruc- Patented Dec. 31, 1968 ture without any lifting of the latter, or interfit with the upper end portions of the prop to an extent such as to require only a very small lift of the superstructure to free it from the prop preparatory to moving it laterally clear of the superstructure.

Certain forms of roof support of the kind specified, such as that described and claimed in my co-pending application Ser. No. 511,511, incorporate props at longitudinally spaced positions adjacent to the rearward and forward ends of the base, there being typically two or possibly three laterally spaced props at the rearward end, and a single prop at the forward end. This latter prop may be of substantially larger diameter than each of the rearward props. Because of this factor, and also because such larger diameter prop usually comprises inner and outer prop units, for example as described and claimed in the specification of my US. Patent No. 3,371,901, which together make the prop substantially heavier than each of the rearward props, its removal by adoption of the conventional arrangement is either impracticable or inconvenient in working conditions underground. It is, moreover, desirable that the length of time necessary to remove such prop, and install a replacement prop, shall be kept to a minimum so as to reduce time delay in resumption of coal-getting operations.

The object of the present invention is to provide an improved roof support of the kind specified which is better adapted to meet these requirements than those hitherto available.

Summary of the invention According to the invention, 1 provide in a roof support comprising a base, a plurality of sockets in said base forming prop seatings, a plurality of props in said seatings, and a roof engaging superstructure carried by said props, the improvement comprising: means defining a lateral entry to at least one of said seatings; said entry extending from a position adjacent to the lower end of the seating to the upper end of the seating, releasable retaining means assembled with the base movable between an operative position preventing withdrawal of one of said props from said seating and an inoperative position permitting withdrawal or entry of said prop from and to said seating, a power-energized means on said support for effecting lateral movement of said prop through said entry, releasable connection means for effecting connection between said power-energized means and said prop.

The term lateral is used herein generically to denote an entry situated at the front, rear, side, or at any intermediate position around the periphery of the socket, the front being the leading end of the support when the latter is undergoing advancement during normal operation of the support. The term socket is to be deemed to include a hole which is open at its lower end as well as a hole which is closed thereat.

The base is preferably provided with a closure member for the lateral entry or each of same, such closure member being movably assembled with the remainder of the base for movement between a closed position and an open or removed position for respectively preventing and permitting passage of the lower end portion of the associated prop therethrough.

A further feature of the invention is that a powerenergized device is preferably provided for moving the prop or each of same through the lateral entry.

Brief description of drawings The invention will now be described, by way of example, with reference to the accompanying drawings wherein:

FIGURE 1 is a view in side elevation showing certain parts of one form of roof support in accordance with the invention;

FIGURE 2 is a plan view of the support shown in FIGURE 1 illustrating also certain modifications which may be made in the construction thereof;

FIGURE 3 is a view in side elevation corresponding to FIGURE 1 and illustrating a second embodiment 01 support in accordance with the invention;

FIGURES 4 and 5 are respectively views in side elevation and in plan view illustrating a third embodiment of support in accordance with the invention;

FIGURE 6 is a plan view of a further embodiment of support in accordance with the invention;

FIGURES 7 and 8 are respectively views in side elevation and in front elevation of a fourth embodiment of support in accordance with the invention;

FIGURE 9 is a view in side elevation of a fifth embodiment of support in accordance with the invention;

FIGURE 10 is a view in side elevation of a sixth embodiment of support in accordance with the invention;

FIGURE 11 is a plan view on an enlarged scale and partly in cross-section on the line 1111 of FIGURE 12 showing in more detail the construction and arrangement of a prop seating in which the lateral opening is forwardly presented and which may be utilized in any of the foregoing embodiments;

FIGURE 12 is a view in side elevation and in crosssection on the line 1212 of FIGURE 11 of the assembly shown therein;

FIGURE 13 is a fragmentary plan view on an enlarged scale of a prop seating and closure member showing in more detail the construction and arrangement of a prop seating in which the lateral opening is presented at the side of the support and which may be utilized in any of the foregoing embodiments, especially in respect of the rearward prop seatings; and

FIGURE 14 is a view in side elevation of the assembly shown in FIGURE 13 with part of the cover member removed.

Description of the preferred embodiment Referring firstly to FIGURE 1, the support comprises a base 10 formed as a hollow structure and consisting of a single base element. This base is a fabricated structure and comprises two laterally spaced elongated chambers 11 of generally rectangular shape in transverse cross-section having raised parts 12 at their rearward ends. A further raised part 13 is situated between the two chambers 11 at their forward ends.

The two chambers 11 may either be joined to each other by a top wall or they may be joined only at their rearward ends, that is to say through the intermediary of the raised parts 12 leaving a medially extending space between the chambers.

The base includes a base plate 14 underlying the chambers 11 including their raised parts 12 and the raised part 13.

The raised part 13 affords a seating for a single, forwardly disposed, prop 15, such seating being formed by provision of a hole in the top wall 16 of the raised part 13. This hole is of a diameter such as to only slightly exceed the external diameter of the prop 15, and the margin of the top wall 16 bordering the hole may be reinforced if desired by an annular, or partly annular, collar welded or otherwise secured thereto.

The base plate 14 is provided with a pad 17 beneath the hole in the top wall 16 and on which the lower end of the prop rests.

The raised parts 12, which may be either separate or joined to each other to form a common raised part at the rearward end of the base, are also formed with seatings for two laterally spaced props 18.

These seatings may be of a diameter providing some lateral clearance with respect to the props 18 and are constituted by holes in the top wall of the raised parts 12. The lower ends of the props 18 rest on underlying portions of the base plate.

Chambers 11 contain traction rams 19, the rearward ends of which are secured in any suitable manner to the base 10 internally thereof, for example by pivoting about horizontal axes, extending transversely of the base to brackets provided therein. The piston rods 20 of these rams are connected to a traction bar 21 which forms, in effect, a forwardly projectable part of the base and to which are fixed slide bars 22 which extend into the interiors of box-section guides 23 afforded by the base.

The traction bar 21 is provided with a connecting element 24 such as an apertured lug enabling it to be connected to a conveyor 25 disposed adjacent to, and extending along, the coal face, for example by means of a bolt or link which is detachable to allow the support to be disconnected from the conveyor when desired.

The props 15 and 18 support a superstructure indicated generally at 26.

This may comprise a rear part 26a in the form of a frame including laterally spaced, longitudinally extending, roof bars connected at their rearward and forward ends by cross members 26b and 260, preferably cranked downwardly so as to define, in combination with the roof bars, a longitudinally extending channel open at least at its forward end.

A further part of the superstructure comprises an elongated beam 26d formed of laterally spaced, longitudinally extending, roof bars preferably of box-shape in crosssection connected to each other at intervals along their length by cross members.

This elongated beam constitutes the fore part of the superstructure and projects forwardly from the rear part to an extent such that it can engage and support the roof above the conveyor 25 and on the face side of the conveyor when, as intended, the support is used in long wall coal mining.

This form of superstructure is more fully disclosed in my co-pending application Ser. No, 511,511.

The rear part of the superstructure is supported by the rearward props 18 and by one of the prop units of the prop 15. The latter is preferably as described and claimed in the specification of my US. Patent No. 3,371, 901 and comprises an outer prop unit 15a formed of telescopically assembled prop sections, and an inner prop unit 15b also formed of two telescopically assembled prop sections and received in, and supported laterally and against downward movement by, the hollow inner section of the outer prop unit. The outer prop unit has a loadbearing element in the form of a yoke 27 incorporating laterally extending arms equipped with upwardly extending projections for engaging in proper seatings 28 at the underside of the rear part of the superstructure. Similar seatings 29 are provided at the rearward end of the rear part of the superstructure for receiving the upper ends of props 18 which are also hydraulic props incorporating telescopically assembled prop sections.

To allow the prop 15 to be removed from the support, or to be moved into a position permitting removal of the inner prop unit 15b, the prop seating afforded by the raised part 13 is formed with an entry presented forwardly of the seating and constituted by a slot 30 in the front wall of the raised part 13, such slot communicating at its upper end with the hole in the top wall 16.

In FIGURES 11 and 12 the construction and arrangement of the raised part 13, the seating formed therein, and a cover member for closing the entry is more fully disclosed.

The raised part 13 is of hollow box-like form and the seating is bounded rearwardly by an approximately semicircular collar portion of channel shape in cross-section and capable of receiving in the channel a rubber liner, such collar portion being welded in an appropriately shaped aperture in the top Wall of the raised part 13.

At its forward side the seating is bounded by a similar semi-circular collar portion 51 welded to a rearwardly extending flange 52 at the upper end of a vertical cover plate 53.

The cover plate has secured to its rearward face a pair of laterally projecting guide plates 54 which engage in internal channels 55 formed in the interior of the raised part 13. The lower margin of the cover plate 53 abuts the rearward face of a transverse bar or ledge 56 welded to the base plate 14 and reinforced by webs 57. The cover member comprising the parts 51 to 53 may be retained in position merely by virtue of its own Weight or a retaining device may be provided if desired. The cover plate 53 is formed medially with a vertical slot 58 to provide clearance for an attachment member 31 on the forward prop 15 as hereinafter referred to.

Adjacent to its lower end, and preferably below the center of gravity of the prop, the latter is provided with the attachment member 31. This attachment member may comprise a collar clamped externally on the prop 15 and furnished with a pair of forwardly projecting vertical lugs apertured to receive a connection pin, such lugs being situated at the forward side of the prop.

The traction bar 21 is also provided with an attachment member 32 which may comprise an upstanding arm rigidly secured to the traction bar and apertured at its upper end to receive a connection pin.

The traction bar may be operatively connected, when desired, with the prop 15 by means of a link 33 apertured to permit of passage therethrough of the connection pins previously mentioned, either or both of which is detachable. The pivotal connection of the link 33 to the prop 15 and to the attachment member 32 provides some degree of constraint against lateral tilting of the prop and this is adequate for prop removal and assembly operations conducted in level workings or where the lateral slope of the floor is only small. Such constraint against lateral tilting is supplemented by the presence of the slide bars 22.

Preparatory to utilization of the traction rams 19 to remove the prop, the conveyor or the section thereof nearest the support concerned would be advanced by utilization of the traction means on the adjacent supports to provide a clearance space forwardly of the support concerned between this and the conveyor. To permit this to be done the traction bar 21 would first be disconnected from the conveyor 25 and after advancement of the conveyor the traction bar would be connected by means of its link 33 to the attachment member 31 of the prop 15.

The superstructure would be temporarily supported by any suitable means, for example mechanical or hydraulic props. These may be placed beneath the yoke 27 which supports the forward end of the rear part of the superstructure and the elongated beam which forms the fore part of the superstructure, and the rear part of which is received in the channel of the rear part of the superstructure may be supported by a packing piece inserted between it and the yoke.

The cover member would be removed from the slot of the raised part 13 and the traction rams 19 energized to project the traction bar 21 forwardly. The link 33 would thus draw the lower part of the prop 15 forwardly out of its seating.

At the rearward side of the traction bar 21 it may be provided with a steadying plate or projection 34 which contacts the bottom face of the prop 15 should the latter tend to tilt rearwardly as it is drawn forwardly out of its seating. This engagement limits the angular movement of the prop and allows it to take up a stable position as shown in broken lines at 15c. The prop may, in this position, be in contact with the floor of the mine working or may be clear thereof.

Ordinarily the drawing of the prop forwardly out of its seating will not cause the prop to tilt rearwardly to the position shown at 150 but this position may be achieved by applying manual force to the upper part of the prop after it has been drawn out of its seating. Alternatively, the traction rams 19 may be energized to withdraw the piston rods rearwardly, thereby bringing the rearward corner of the prop 15 at its lower end into contact with the floor of the mine working and producing tilting under power to the position shown at 150. This movement is limited, as previously mentioned, by contact with the plate or projection 34.

From this position the prop 15 can be removed as a whole from the support without obstruction due to interengagement between the prop and the yoke or the inner prop unit and a seating in which the latter engages at the underside of the elongated beam which forms the fore part of the superstructure.

Alternatively if only the inner prop unit is required to be removed it can be withdrawn from the outer prop unit when the prop is in the position shown at 150.

To reassemble a prop in the forward seating of the base the replacement prop which is required to be so assembled may conveniently be connected to the link 33 when the traction bar is in the fully forward position. Such prop may be inserted while it is inclined forwardly as indicated at 15d and then may stand on the floor of the mine working in an upright position as indicated at 15e while connection is made to the link 33. Thereafter the traction rams may be energized to retract the piston rods. This initially tilts the prop to a rearwardly inclining position as shown at 15 and continued rearward movement of the traction bar by the rams will cause the lower end of the prop to ride over the upwardly projecting lip of the base plate 14. Thereafter engagement of the rearward side of the prop with the collar portion 50, while retraction of the piston rods of the rams is continued, will bring the prop to an upright position in its seating as shown in full lines at 15.

If desired the upturned lip at the forward end of the base plate 14 may be dispensed with and a ramp may be provided leading up to the pad 17 to facilitate entry of the lower end of the prop into the seating.

The raised parts 12 which incorporate the seatings for the rearward props 18 may, if desired, be provided with entries at the outer sides of the raised parts 12, as indicated at 35. Such entries are normally closed by cover plates which can be secured in position in any suitable manner and which incorporate top wall portions engaging the props 18 to maintain these in a stable upright position when the cover plates are themselves in position on the base.

The construction and arrangement of the seatings in the raised parts 12 and the cover plates for the entries thereto, which are presented to the adjacent side of the base, is illustrated in more detail in FIGURES 13 and 14.

The raised part 12 is provided with a semi-circular collar portion 60 similar to the collar portion 50 already described with reference to FIGURES 11 and 12 welded to the top wall of the raised part and forming the inner boundary of the seating.

The outer boundary of the seating is formed by a further collar portion 61 having a semi-circular inner face and having lugs 62 which engage in guideways afforded by respective channel-section blocks 63 welded to the upper wall of the raised part 12.

The side wall of the raised part 12 is formed with a slot 64 forming the lateral entry to the seating and this is normally closed by a removable cover member 65 which serves also to prevent outward lateral displacement of the collar portion 61. To retain the cover member releasably in its closed position a pair of lower blocks 66 are welded to the outer face of the raised part 12 but spaced outwardly therefrom to provide gaps in which marginal portions of the cover member 65, as indicated at 67, are received.

A further pair of upper blocks 68 are welded to the outer side face of the raised part and are spaced laterally outwardly of adjacent faces of the channel-section blocks 63 to provide gaps in which lugs 69 at the upper end of the cover plate are received.

In this particular arrangement the lower ends of the rearward props 18 can be withdrawn laterally outwardly through the entries upon removal of the cover members 65 and collar portions 61.

In the construction illustrated in FIGURE 3, parts corresponding to those already described are designated by like numerals of reference with the prefix 1 and the preceding description is to be deemed to be applicable thereto.

In this construction the raised part 113 has its entry formed at the rearward side of the raised part instead of at the forward side.

A longer link 133 releasably connected at one end at least between the attachment member 131 on the prop and the traction bar 121 is of longer form and serves to displace the lower end of the prop rearwardly from its seating in the raised part 113 upon contraction of the traction rams 119, so that the prop either takes up or can be tilted to the position indicated at 1150. The inner prop unit 1151? can be removed forwardly when desired, as shown.

In the construction illustrated in FIGURES 4 and 5 parts corresponding to those previously described are designated by like numerals of reference with the prefix 2 and the preceding description is to be deemed to be applicable thereto.

In this construction the seatings in the raised parts 212 are formed with entries at their forward sides normally closed by closure plates but removable to permit the rearward ends of traction rams 219 to be connected when required to the lower ends of the props 218.

The entries and closure plates may be of the same general construction as has already been described with reference to FIGURES 13 and 14.

The traction rams 219 are shown connected to the lower ends of the props, but it will be understood that when the support is in use normally the rearward ends of the rams would be connected to a suitable fixed anchorage. Such anchorage could be situated internally of the raised parts 12, in which case the cover members would include openings through which the rearward end portions of the rams project. Connection to such fixed anchorage would be releasable to permit the rams to be connected, when desired, to the lower ends of the props.

Upon removal of the cover plates the props 218 can be drawn forwardly out of their seatings through the entries by energizing the traction rams to contract same, the piston rods 220 and traction bar 221 being held against rearward movement by connection to the conveyor 225 through the intermediary of the connecting element 224.

The forward prop 215 can also be withdrawn forwardly in the same manner as is illustrated in FIGURES l and 2, a link 233 being provided for this purpose connectable by a removable connection pin at its rearward end to the attachment member 231 on the forward prop.

Preparatory to removal of either of the props 218 by the traction rams 219, the rear part of the superstructure would be temporarily supported, for example by a hydraulic or friction prop interposed between the floor or a part of the base and the superstructure, at a position which does not obstruct removal and replacement of the prop 218 concerned.

In the construction illustrated in FIGURE 6 parts corresponding to those already described are designated by like numerals of reference with the prefix 3 and the preceding description is to be deemed applicable thereto.

In this construction the rearward props 318a are mounted in seatings formed in lateral extensions of the raised part at the rearward end of the base. Such seatings have forwardly presented entries but the props are removable manually therethrough.

The lateral extension of the base is continued forwardly to provide additional seatings for the accommodation of temporary props 340 which may be either hydraulic or mechanical and which are placed beneath the arms of the yoke to provide temporary support to the superstructure during removal of the forward prop 315.

In the construction illustrated in FIGURES 7 :and 8 parts corresponding to those already described are designated by like numerals of reference with the prefix 4 and the preceding description is to be deemed to be applicable thereto.

This support is generally similar to that illustrated in FIGURES 1 and 2 but additionally is equipped with auxiliary support means for supporting the forward end of the rear part of the superstructure and the elongated beam which forms the fore part of the superstructure preparatory to, and during, reassembly of the forward prop 415.

These auxiliary support means comprise a pair of hydraulic rarns 470 disposed adjacent to respective opposite sides of the support and pivotally connected at their lower ends to brackets 471 on the raised part 413 of the base. The brackets 471 include upwardly projecting socket portions 471a open at their forward sides to enable the rams to be received therein when in an upright position 48 as hereinafter described, in which position the socket portions 471a provide steadying for the rams against lateral tilting. At their upper ends the projecting piston rods of the rams 470 are pivotally connected to a cross member 472 which underlies the forwardly projecting part 4260! of the superstructure. Ordinaril the rams 470 incline upwardly and forwardly from their lower ends and provide, through the intermediary of the cross member 472, auxiliary support to the forwardly projecting part 426d of the superstructure. Forward displacement of the cross member 472 is prevented by a tie member 473 which may be in the form of a cable encircling the upper end of prop 415 or an articulated tie member. This constitutes the normal operating position of the rams 470. The rams together with the cross member can be moved rearwardly in a pivotal manner about axes defined by the pivotal connection of the rams to the bracket 471 so that the rams are then in an upright position as shown in chain lines.

Retraction of the piston rods of the rams allows the cross member to be brought into a position beneath the forward cross member 4260 of the rear part of the superstructure, and consequently pressurization of the rams 470 provides support to the forward end of the rear part of the superstructure allowing the prop 415 to be safely removed. The elongated beam which forms the fore part of the superstructure may also be supported by a packing piece inserted between the cross member 4260 and the underside of such beam.

The rams 470 also act as upper lateral guide members which would prevent lateral tilting of the prop 415 during removal and reassembly should this operation require to be undertaken in mine workings which present a slope in a direction laterally of the support.

In the construction illustrated in FIGURE 9 parts corresponding to those already described are designated by like numerals of reference with the prefix 5 and the preceding dsecription is to be deemed applicable thereto.

In this construction support to the forwardly projecting part of the elongated beam which forms the fore part of the superstructure is augmented by provision of a forward base element 510a. Such base element affords a seating adapted to receive a prop which conveniently is constituted by the inner prop unit 515b of the composite prop 515.

To permit removal of the prop 515 and extraction of the inner prop unit 515b therefrom by connection to the outer prop unit 515a of the link 533, an anchorage element in the form of a chain 574 is provided. Such chain can be connected between the upper end of the cylinder of the inner prop unit 515b and an anchorage element on the cross member 52612 at the rearward end of the rear part 526a of the superstructure.

When the traction rams 519 are energized to move the traction bar and bracket 532 forwardly the chain 574 restrains forward movement of the inner prop unit and this is withdrawn from the outer prop unit 515a, as shown in chain lines in FIGURE 9, and can thereafter be erected manually as shown in dashed lines in the forward base element 510a.

The latter may be connected to the rearward base element 510 by connecting bars 575 which are either rigidly connected to both base elements or pivotally connected thereto about respective horizontal axes extending transversely of the base elements.

In the construction illustrated in FIGURE 10 parts corresponding to those already described are designated by like numerals of reference with the prefix 6 and the preceding description is to be deemed applicable thereto.

This construction is generally similar to that illustrated in FIGURES 1 and 2 but in this case the traction bar 621 is provided with a pair of laterally spaced upstanding attachment members or brackets 632, each of which is furnished with a long connecting link 633 for connection to an attachment member or bracket 631 near the upper end of the cylinder of each rearward prop 618 to permit either of the latter to be drawn out of their seatings when required. In this case the raised parts 612 of the base element would have frontal walls formed with entries to permit withdrawal of the props and such entries may be closed by removable cover plates, the arrangement being generally as described with reference to and as illustrated in FIGURES 13 and 14.

The successive positions occupied by one of the rear props 618 during withdrawal are indicated in chain lines at 618a and 6182).

I claim:

1. In a roof support for underground mine workings comprising a base, a plurality of sockets in said base forming prop seatings, a plurality of props in said seatings, and a roof engaging superstructure carried by said props, the improvement comprising:

(a) means defining a lateral entry to at least one of said seatings,

(b) said entry extending from a position adjacent to the lower end of the seating to the upper end of the seating,

(c) releasable retaining means assembled with the base movable between an operative position preventing withdrawal of one of said props from said seating and an inoperative position permitting withdrawal or entry of said prop from and to said seating,

(d) a power-energized means on said support for effecting lateral movement of said prop through said entry, and

(e) releasable connection means for effecting connection between said power-energized means and said prop.

2. A support according to claim 1 wherein:

(a) at least said one seating comprises an upwardly presented surface on said base to engage and support the lower end of said one prop, and

(b) said upwardly present surface and the lower end of said one prop are slidably engaged with each other for unobstructed relative lateral movement of said one prop at its lower end.

3. A support according to claim 1 wherein:

(a) said power energized means comprises at least one traction ram arranged longitudinally of said base and including piston and cylinder components movable relatively in response to the admission of fluid under pressure to said ram,

(b) a forwardly projectable part is provided at the forward end of said base and is connected to one of said ram components for movement thereby in a direction longitudinally of said base,

(c) said releasable connection means includes means for connecting said projectable part to said prop to enable at least withdrawal of same to be effected under power from said entry.

4. A support according to claim 3 wherein:

(a) said prop is disposed in a seating adjacent to the forward end of said base,

(b) said releasable connection means includes means constraining said prop against tilting in a vertical plane extending transversely of said base during withdrawal from said entry while permitting said prop to tilt in a vertical plane extending longitudinally of said base,

(c) stop means are provided to limit the extent of tilt from a vertical position of said prop in said longitudinally extending vertical plane at least during withdrawal thereof from said seating through said entry.

5. A support according to claim 4 wherein:

(a) said connection means comprises a link pivotally connected to said forwardly projectable part and to said prop adjacent to the lower end of the latter but spaced upwardly therefrom,

(b) said prop is spaced rearwardly from said forwardly projectable part when said prop is in a vertical position,

(c) said link permits said prop to be tilted to incline in a direction upwardly and rearwardly from the lower end of said prop to an extent limited by engagement of said lower end of said prop with said forwardly projectable part.

6. A support according to claim 3 wherein:

(a) said prop comprises a hollow outer prop unit and an inner prop unit received in the interior of said outer prop unit,

(b) said inner and outer prop units support respective parts of said superstructure,

(c) anchor means are provided releasably connectable between said inner prop unit adjacent to the upper end thereof and a part of said support situated rearwardly of said prop for restraining withdrawal of said inner prop unit and thereby enabling separation of said inner and outer prop units to be effected upon withdrawal of the latter.

7. A support according to claim 1 wherein:

(a) said base includes laterally spaced seatings for rearwardly disposed ones of said props,

(b) each of said seatings has its entry presented at the frontal side of said seating,

(c) said releasable connection means includes means for selectively connecting said power-energized means with either of said props.

8. A support according to claim 3 wherein:

(a) at least one auxiliary supporting element is provided for supporting said superstructure at an elevated position preparatory to and during withdrawal of said one of said props,

(b) said auxiliary element comprises a pressure fluid energized ram operatively connected between said base adjacent to the forward end of the latter and extending upwardly therefrom to a position beneath said superstructure.

References Cited FOREIGN PATENTS 1,331,567 5/ 1963 France.

983,079 2/1965 Great Britain. 1,001,411 8/ 1965 Great Britain.

JACOB SHAPIRO, Primary Examiner.

US. Cl. X.-R. 

